Explosive composition



Patented Apr. 29, 1952 UNITED STATES PATENT OFFIC EXPLOSIVE COMPOSITION John E. Riley, Flanders, N. J., assignor to Hercules Powder Company, Wilmington, Del., a

corporation of Delaware No Drawing. Application November 22, 1950, Serial No. 197,165

Claims.

convenient to use, while at the same time retaining its high explosive strength. Its sensitiveness to shock is illustrated by the fact that a shot from a rifle explodes nitroglycerin, even when fired from a distance of about 500 feet. Blasting gelatin, because of its high strength, its reasonably high density, and high order of detonation, is an explosive well suited for demolition work or other uses where brisance is desirable. It was discovered by Nobel in 1875 and is normally a solid colloidal solution of nitroglycerin (90-93%) and nitrocellulose (7-10%). The nitrocellulose used in making blasting gelatin usually has a nitrogen content of about 12.0- 12.4% and is of the highest viscosity obtainable consistant with other requirements which must be satisfied. For example, its viscosity is so much greater than that of so-called 1000-second viscosity nitrocellulose that the standard viscosity determination is not applied to it; it is tested by the so-called blasting gel test. The resulting elastic mass is less sensitive to shocks and blows than liquid nitroglycerin or even guhr dynamite. However, the sensitivity to shock is still too great for safety in certain uses.

Smaller amounts of nitrocellulose than the proportion used in blasting gelatin have been j used to give softer, even fluidlike, masses of nitrotinby means of nitrated aromatic hydrocarbons, r

such as monoand di-nitrotoluene, or by the use of camphor. In order to get the desired degree of insensitiveness in such powders, it is necessary to add a considerable amount of the desensitizer with resultant loss of explosive strength of the 2 powder and loss of the ability to shoot with the required high order of detonation.

Foricertain uses, including military operations, .oil well blasting, etc., there is a need for an insensitive blasting gelatine having high explosive brisance; i. e., high strength, reasonably high density, and a high order of detonation.

To be suitable for military use, for example, an explosive must be safe from possible detonation by accidental impact met in the storing and handling of large lots of materials, and, also,

it must be insensitive to the impact of rifle fire from relatively short distances 'of the order of about feet. It must be of such stability that it can be stored for fairly long periods of time, possibly at elevated temperatures, such as are found in the hold of a ship.

Now in accordance with this invention, a stable blasting explosive has been discovered which is highly insensitive to such impact and which contains cellulose acetate as the desensitizing agent. l

Generally described, the present invention is a detonative explosive composition comprising at least one liquid explosive nitric ester and as a gelling agent for said ester, from about 4% to about 10% by weight thereof of cellulose acetate having a viscosity not greater than about 80 secondsand a combined acetic acid content of between about 54.0% and about 56.0%.

If th'cellulose acetate employed has a viscosity of above about 80 seconds, it has been found that satisfactory gelation is not obtained. Furthermore, it the cellulose acetate has a combined acetic acid content oi less than about 54.0% or greater than about 56.0%, satisfactory gels are not obtained. Less than about 4% of any operable" type of cellulose acetate, based on the weightof the liquid explosive nitric ester, does not effect the desired insensitivity, while the incorporation of more than 10% of the acetate results a composition which is too insensitive for proper initiation and propagation.

Having now indicated in a general way the natureand purpose of the invention, the following examples are given for the purpose of illustration, Unless otherwise indicated, the explosive compositions of the examples were mixed in a figure eight bowl at a temperature of about 120. R, the cellulose acetate was first added to the liquid explosive nitric ester and pregelled for 5 minutes, and the dope ingredients were then added and mixed for from 2 to 5 minutes. In Example 5 only, the nitrocellulose employed was added after the cellulose acetate and mixed for 1 minute.

Blasting explosives desensitized with cellulose acetate 4. Er- 1311- Ex- Ex- Exomnm Izunple l ample 2 ample 3 ample 4 ample 5 N itroglycerin/Ethylcne Glycol Dinitratc (60 :40) percent. 42. 42. 0 l2. 0 42. l 42. 0 Cellulose Acctate .do 2. 0 3. 0 4. 0 3. 0 3. 0 Cellulose Nitrnte do 0. Sodium Nitrate.. do. 45. 0 45. 0 45. 0 15.0 44. 5 Wood Pulp. do 3. 0 2. 5 2.0 2. 5 2. 5 Ivory Meal. do. 5. O 4. 5 4. 0 6. 5 I. 5 Starch... o 2. 0 2.0 2. 0 Chalk... o. 1.0 1.0 i 1.0 Zinc Oxide .do. l 1.0 l 0 Count, 1% X 8" 04. 0 97. 0 Sensitivencss (Gap I 'l e s t N o. 8 Cap" .inches 2. 0 0. 0 Failed 4. 0 6.0

1 Hercules Powder Company, grade LL-l which has a viscosity of 2 to 4 seconds d a combined acetic acid content of 55.0 to 56.0%. This material we. crccued to remove mate 2 This powder ropagated completely cartridges butted crimp to crimp.

A standard explosive composition lest known as the halved cartridge gap method which is described fully in Bulletin 346, issued by the U. S. Bureau of Mines.

coarser than 30-inesh. ugh three 14 X 8 Example 6 A blasting explosive was prepared having the following formula. The cellulose acetate employed had a viscosity of 25 to 50 seconds and a combined acetic acid content of 54.0 to 55.0%.

Nitroglycerin per cent 42.0 Cellulose acetate do 3.0 Sodium nitrate do 45.0 Wood pulp do 2.5 Ivory meal do 6.5 Zinc oxide do 1.0 Count 92.0 Sensitiveness (Gap Test) No. 8 Cap 6" (failed at 8") A firm gel was obtained.

Example 7 A blasting explosive was prepared having the following formula. The cellulose acetate employed had a viscosity of 60 to 80 seconds and a combined acetic acid content of 54.0 to 55.0%.

A very firm gel was obtained. The gel was slightly leaky but was satisfactory, comparing favorably in respect to leakiness with regular gelatinous dynamite.

Example 8 Three compositions were prepared, each having the following nominal formula.

' Per cent Nitroglycerin J 42.0 'Celluloseacetate 2.0 Sodium nitrate 45.0 Wood pulp 3.0 Ivory meal" 5.0 Stretch.. v Chalk.

In the first composition the cellulose acetate employed had a viscosity of 12 to 20 seconds and a combined acetic acid content of 52.5 to 53.5%; the second, a viscosity of 85 seconds and a combined acetic acid content of 52.0 to 53.5%; the third. a viscosity of A; to 2 seconds and a combined acetic acid content of 60.6 to 62.1%. None of these compositions formed a gel.

Example 9 Cellulose acetate of a particle size enabling to pass through a 30-mesh screen was added to nitroglycerin in an amount sufiicient to constitute 7% by weight of the liquid explosive nitric ester. The particular cellulose acetate employed had a viscosity of 8'? seconds and a combined acetic acid content of 54.8%. The mixture was stirred for 5 minutes at 70 F. The temperature was raised to 110 F. and the mixture was stirred for an additional 8 minutes. No gelation occurred. Therefore, no dope ingredients were added.

The blasting explosives of Examples 1'? contain about 40% of a highly explosive nitric ester of a polyhydric alcohol or a mixture of two or more such esters which, in the liquid state, is highly sensitive to shock. The 60:40 nitroglycerin/nitroglycol mixture is a preferred combination because of its high explosive strength, low freezing point, and ease of gelatinization. However, other combinations of nitroglycerin and nitroglycol may be utilized or either one may be used with still other similar highly explosive nitric esters, such as nitroisobutylglycerin trinitrate, and the like.

It is preferred to employ the cellulose acetate in a particle size which gels rapidly. It is especially preferred that the cellulose acetate be of a particle size enabling the major portion thereof to pass through a 30-mesh screen. Larger particles are operable but gelling time is increased as the particle size increases.

Sodium nitrate is an oxygen-supplying inorganic salt which is normally used in gelatinous dynamites in an amount ranging from about 0% to about 60%, dependent upon the explosive strength desired. Ammonium nitrate, potassium chlorate, etc., as well as mixtures such as sodium nitrate and ammonium nitrate likewise are materials operable for this purpose.

Nitrocellulose may be included, Example 5 being illustrative, to insure that nitroglycerin will not exude from the absorbent. It may be found desirable to employ a small amount or nitrocellulose for this purpose, especially when the cellulose acetate employed is in the upper portion of the operable viscosity range.

Chalk, starch, zinc oxide, and ivory meal are incorporated in small amounts for their usual properties. A small amount of wood pulp or similar substance is used to aid in adjusting the stickiness of the formulation, the desired characteristics of the explosive being dependent upon the intended use.

The use of cellulose acetate as the desensitizing agent has the advantage over such conventionally employed substances as dinitrotoluene, camphor, and the like, of having less adverse effect on the explosive strength of the resulting explosive. Because of its greater desensitizing action, less cellulose acetate is required to give the same degree of insensitiveness obtained by the above-mentioned known agents. Cellulose acetate is nonexplosive and noninflamrnable so that no undue precautions need be taken in handling this material.

Where in the specification and appended claims the term viscosity is used, it is meant to designate a characteristic of the cellulose acetate as defined by a standardized method for viscosity determination and which, briefly described, consists of making a solution (by weight) of the cellulose acetate dissolved in a solvent composed of 90:10 acetone/ethanol (by weight). This material is held in a one-inch diameter tube at C. and the viscosity values are an expression of the time of fall, in seconds, of a 1%" steel ball through ten inches of the solution. For conversion purposes a viscosity of one second is equivalent to 377 centipoises.

This application is a continuation-in-part of application Serial No. 687,227, filed July 30, 1946, now abandoned.

What I claim and desire to protect by Letters Patent is:

1. A detonative gelatinous explosive composition'comprising at least one liquid explosive nitric ester and as a gelling agent for said ester, from about 4% to about 10% by weight thereof of cellulose acetate having a viscosity not greater than about 80 seconds and a combined acetic acid content of between about 54.0% and about 56.0%.

2. A detonative gelatinuous explosive composition according to claim 1 in which the liquid explosive nitric ester is nitroglycerin.

3. A detonative gelatinous explosive composition according to claim 1 in which the liquid explosive nitric ester is a mixture of nitroglycerin and nitroglycol.

4. A detonative gelatinous explosive composition comprising an oxygen-supplying inorganic salt, at least one liquid explosive nitric ester and as a gelling agent for said ester, from about 4% to about 10% by weight thereof of cellulose acetate having a viscosity not greater than about 80 seconds and a combined acetic acid content of between about 54.0% and about 56.0%.

5. A detonative gelatinous explosive composition according to claim 4 in which the liquid ex-.

plosive nitric ester is nitroglycerin.

6. A detonative gelatinous explosive composition according to claim 4 in which the liquid explosive nitric ester is a mixture of nitroglycerin and nitroglycol.

7. A detonative gelatinous explosive composition comprising from about 17% to about of an oxygen-supplying inorganic salt, from about 20% to about of at least one liquid explosive nitric ester, and as a gelling agent for said ester, from about 4% to about 10% by Weight thereof of cellulose acetate having a viscosity not greater than about seconds and a combined acetic acid content of between about 54.0% and about 56.0%.

8. A detonative gelatinous explosive composition according to claim 7 in which the oxygensupplying inorganic salt is sodium nitrate.

9. A detonative gelatinous explosive composition according to claim 7 in which the liquid explosive nitric ester is nitroglycerin.

10. A detonative gelatinous explosive composition according to claim 7 in which the liquid explosive nitric ester is a mixture of nitroglycerin and nitroglycol.

. JOHN E. RILEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 242,783 Lewin June 14, 1881 649,852 Luck May 15, 1900 2,001,212 Olsen May 14, 1935 2,201,640 Weldin 'May 21, 1940 FOREIGN PATENTS Number Country Date 24,662 Great Britain A. D. 1898 290,866 Italy Dec. 1, 1931 OTHER REFERENCES Heuser, "Cellulose Chemistry," published (1944) by John Wiley & Sons, New York, pp. 257 and 273. 

1. A DETONATIVE GELATIONOUS EXPLOSIVE COMPOSITION COMPRISING AT LEAST ONE LIQUID EXPLOSIVE NITRIC ESTER AND AS A GELLING AGENT FOR SAID ESTER, FROM ABOUT 4% TO ABOUT 10% BY WEIGHT THEREOF OF CELLULOSE ACETATE HAVING A VISCOSITY NOT GREATER THAN ABOUT 80 SECONDS AND A COMBINED ACETIC ACID CONTENT OF BETWEEN ABOUT 54.0% AND ABOUT 56.0%. 